Support is requested for a Gordon Research Conference on "Membrane Transport Proteins: Physiological and Pathophysiological Implications," to be held from October 3 to 8, 2004 at Les Diablerets, Switzerland, as well as the 2006 Membrane Transport Proteins conference to be held during the summer of 2006. These will be the fourth and fifth Gordon Research Conferences on this topic since the series started in 1998. The fast-evolving field of membrane transport proteins is currently one of the most exciting in the biomedical sciences. Membrane transport proteins play fundamental roles in cell function, regulating and maintaining a constant intracellular environment, and are also major targets in the treatment of human disease. The neuronal serotonin and norepinephrine transporters are targeted by antidepressant and antianxiety medications. The dopamine transporter is targeted by drugs such as methylphenidate used to treat attention-deficit disorder as well as the widely abused psychostimulants cocaine and amphetamine. The gastric H+ATPase is inhibited by Omeprazole in the treatment of gastric ulcer. The human multidrug resistance P-glycoprotein, a member of the ABC superfamily, plays a role in the failure of cancer chemotherapy through its ability to export hydrophobic cytotoxic drugs from cells, and inhibitors may prove valuable for the development of more effective cancer treatments. Recent developments that will be presented and discussed at the meeting hold wide-ranging implications for both basic science and clinical practice. Sessions will cover neurotransmitter transporters and their association with human psychiatric disorders; ABC transporters and human disease; regulatory mechanisms, structural biology and structure/function of ATPases, channels and transporters; organization of transporters into multimeric complexes; novel transporter families; and transporters in intracellular organelles and paracellular transport. This program will bring together a group of scientists from many different specialties, including biochemistry, biophysics, cell and molecular biology, molecular and cellular endocrinology, signal transduction, molecular pharmacology, and genetics. The meeting will consist of 2 plenary talks, 41 regular talks, poster presentations and short talks by young investigators selected from the abstracts. Discussants will provide an introduction and stimulate discussion during their sessions. All 47 speakers and discussants have committed to attend the meeting. Talks will be prepared for a diverse audience comprised of students, postdoctoral scientists and fellows, and academic and pharmaceutical industry scientists. In keeping with the GRC tradition, the interactions that will result, whether from formal or informal discussions, can be expected to be extraordinarily stimulating and productive.